This application relates to the art of cutting devices and, more particularly, to improvements in tools for cutting workpieces having a circular cross section such as tubing. Although the preferred embodiment will be described in connection with a manual tubing cutter apparatus for cutting plastic tubes by hand, it is to be appreciated that the invention has application in other areas including devices for cutting, clipping, or otherwise applying a force to associated workpieces.
A wide variety of tubing cutters has been provided heretofore for cutting plastic tubing of the character used in commercial and domestic water systems, such as schedule 40 PVC tubing, for example. Such cutters have included scissors-type cutters such as that shown in U.S. Pat. No. 6,513,245 to Aubriot and U.S. Pat. No. 6,658,738 to King wherein a tube to be cut is supported in a cradle portion of the cutter and a blade is displaceable about a fixed pivot axis to cut a tube interposed between the cradle and blade. In the King patent, the pivot axis is adjustable to accommodate the cutting of tubes of different diameter.
The scissors-type cutters which require a squeezing action of the handles requires an excessive effort on the part of the user to achieve a cutting operation, especially with larger diameter tubing. Partly in this respect, these tools require the user to rock or rotate the tube and cutter in opposite directions while squeezing the handles to apply a cutting load. Furthermore, with initially cutting through a larger diameter tube, a user who has a small hand span has difficulty in applying the necessary closing force on the handles to achieve initial cutting of the tube and, often, has to grasp the handles with both hands to initiate cutting.
Another type of tubing cutter heretofore available includes a cradle for supporting a tube to be cut and a pivotal cutting jaw or blade which is intermittently displaced toward the cradle by means of a ratchet mechanism. While the ratchet mechanism allows a smaller stroke of the cutter handles relative to one another for each intermittent cut, whereby a user can operate the cutter without a large hand span, the cutters are structurally complex and a cutting operation requires a number of sequential displacements of the ratchet handle relative to the cutting head to complete a cutting operation, especially with respect to larger diameter tubes. Accordingly, more work and time is required than is desirable.
In addition to such tubing cutters, a number of metal shears and pruning devices have been provided in which manipulation of the handles of the cutters provide for a slicing displacement of a cutter blade relative to an anvil surface or the like against which an object is pressed during the cutting operation. Such shears are shown, for example, in U.S. Pat. No. 2,508,790 to Herr, U.S. Pat. No. 2,528,816 to Boyer, and U.S. Pat. No. 2,564,154 to Compton. These cutting devices are characterized by a pair of handles pivotally interconnected with one another, a cutter blade pivotally attached to one of the handles and a mechanism such as a pin and slot arrangement between the blade and the other handle by which the blade is displaced in a shearing and slicing motion in response to closure of the handles relative to one another. The angular blade travel during cutting with shears of this character is less than the angular displacement required to close the handles relative to one another, whereby the diameter of an object to be cut is limited in order to provide for a user to grasp and close the handles with just one hand. Further, cutting is achieved by a combination of shearing and slicing motions, whereby the force required on the handles to achieve cutting is very uniform throughout the cutting stroke.